1. Field of the Invention
The present invention is directed to a system and method for producing partitioned tubular film packages that retain different materials on either side of a partition, and more particularly, to a method of producing mine roof bolt resin packages in which a polymerizable resin component and a catalyst component are retained on opposing sides of a partition in a tubular package.
2. Description of Related Art
Mine roof bolts and other structural elements are often anchored into rock, concrete or the like, by a combination of adhesives and mechanical structures such as an expansion anchor at the distal end of the bolt. Bolts sized ⅝ inch to 1¼ inch in diameter are used in boreholes varying from ¾ inch to 2 inches in diameter. Adhesives are generally formed in place within the borehole by providing a resin cartridge that includes two compartments, with a polymerizable (curable) resin in one compartment, and a hardener or catalyst in another compartment. A borehole is drilled in the rock, and the cartridge containing the polymerizable resin and catalyst is inserted into the blind end of the borehole. When a mine roof bolt is inserted into the borehole, the distal end of the bolt ruptures the package so that the resin and catalyst are mixed. Rotation of the bolt about its longitudinal axis mixes the resin and catalyst. The bolt becomes fixed within the resin upon curing.
In these two component packages, it is critical that the polymerizable resin and the catalyst are maintained separate from each other until the package is ruptured during installation of the mine roof bolt. Some resin cartridges include an inner compartment containing catalyst surrounded by an outer compartment containing the polymerizable resin. Other resin cartridges employ a barrier to divide a container into two compartments with the catalyst and resin on opposing sides of the barrier. In an aggressive environment, such as an underground mine, resin cartridges are often produced from strong films such as polyethylene terephthalate, such as Mylar®. Polyethylene terephthalate provides the desired structural integrity to the resin cartridge, yet is more costly than other pliable films that may be used in less aggressive environments. Conventional resin cartridges often use polyethylene terephthalate for the outer compartment as well as the inner compartment or the barrier, even though these inner structures are not exposed to the underground mine environment and do not require the structural integrity of the outer compartment.
The resin component and the catalyst component may each include filler material in the form of particulate matter. Filler material is used to increase the volume of the package at a low cost compared to the cost of additional reactive components and to control viscosity of the components. The resin cartridges are formulated by balancing the mass of liquid and solids and the particle size of solids to achieve good anchorage. If the viscosity or size of the filler is incorrect, the bolt may be difficult to insert into the borehole or the bolt may be inserted into the borehole, but with poor mixing of the resin and catalyst. The amount of filler, type of filler and size of the filler is important to obtain proper performance under a variety of applications. Using filler that has only very fine particulate matter may result in a product that does not sufficiently shred the tough packaging material. U.S. Pat. No. 4,616,050 (incorporated herein by reference) describes the use of filler with a minimum particle size of 1 mm and describes appropriate ratios of filler size to the annulus dimension between the bolt and borehole. Excess coarse filler in a resin cartridge can result in a product through which it is difficult to properly insert a bolt. In general, bolts that are sized similar to the diameter of the borehole use resin cartridges with a smaller particle size than filler that is used in resin cartridges for bolts that are much smaller in diameter than the borehole.
Upon insertion of the bolt into a borehole, the bolt is rotated to shred the package and enhance mixing until the resin hardens to a degree that nearly prevents the bolt from being rotated, and the resin is allowed to cure. If the mass of the fillers or liquid resin is incorrect, only a portion of the resin may harden. Since it is essentially difficult to determine the degree of hardening of the resin in the borehole, it is desirable that every cartridge have the correct amount of resin, filler, filler particle size, and catalyst and that every cartridge be the same and be formulated to achieve the optimum performance for each application.
Resin cartridges are produced via a variety of techniques. In general, these techniques involve advancing a web of a film into a tube shape having a divider within the tube, thereby producing a partitioned tube. One compartment of the partitioned tube receives the resin composition and the other compartment of the partitioned tube receives the catalyst composition. The tube is sealed off at intervals to produce lengths of the filled package.
The partitioned package is filled in a packaging machine that receives a stream of a curable resin composition into one compartment and a stream of catalyst composition in the other compartment. The resin composition and the catalyst composition are prepared in separate mixing vessels and are transferred to the packaging machine. The preparation and transfer of the resin composition and the catalyst composition has conventionally been conducted in batch operations or semi-continuous operations with minimal feedback or process controls.
Accordingly, a need exists for a resin cartridge production system that operates on a continuous basis with enhanced process controls for adjusting the compositions of the resin and catalyst components.